Nitrogen losses from perennial ryegrass and plantain monoculture swards following seasonal applications of dairy cow urine: A lysimeter study

In grazed pasture-based systems, urine patches are a major source of nitrogen (N) loss to the environment. A soil lysimeter study was conducted to evaluate the effectiveness of ribwort plantain (Plantago lanceolata L.; PL) in reducing N leaching from dairy cow urine deposits relative to perennial ryegrass (Lolium perenne L.; PRG). The study was conducted over 3 consecutive years (2020 – 2023). In year one, the swards were in the establishment phase (< 18 months) following reseeding, in years two and three swards were established. Urine was applied to PL and PRG monocultures on both a free draining Cambisol and a poorly draining Gley soil in either autumn or spring for year 1 and 2. In year 3, urine was applied to the same treatments in either autumn or winter. Plantain showed no ability to (P > 0.05) reduce total nitrogen (TN) leached during the establishment phase or within spring applications relative to PRG. Established PL (year 2 and 3), within the autumn/winter treatments, consistently reduced TN leached by an average of 23 % (236 vs 308 kg TN ha⁻¹) across the three applications relative to PRG. This study has demonstrated that established (>18 months old) PL monocultures can be utilised to reduce N leaching loss. Variation in results recorded over the duration of this experiment highlight that many factors are associated with the impact of PL on N leaching from pasture, relative to PRG. Further research is required to evaluate the effectiveness of PL at farm systems level to reduce N leaching.